1. Field of the Invention
The present invention is directed to the field of automotive airbag deployment systems and more specifically to the area of diagnostic systems for detecting faults within the air bag deployment circuit.
2. Background Information
As discussed in commonly assigned U.S. Pat. Nos. 4,359,715 and 4,366,465 (incorporated herein by reference), it is important to provide a diagnostic subsystem for an airbag deployment system that continually checks the continuity of the circuit which comprises the wiring harness, electrical connectors, various crash sensors and electrically responsive explosive igniters (squibs). The igniters are conventionally wired to associated electrical connectors that provide shorting paths around the igniters when the connectors are disconnected (unmated). Such shorting insures that voltages induced into the wiring of a disconnected igniter will not accidentally energize the igniter and cause accidental airbag deployment. The diagnostic system of the aforementioned patents senses for shorts and provides an alarm to the vehicle operator to warn of disconnected connectors and other faults which would constitute an inoperable system.
In such a diagnostic system, each crash sensor switch is shunted by a known resistance value and the electrical igniter constitutes a known resistance value. The diagnostic system provides a low current through the igniter and crash sensor circuit and detects changes in voltage levels that appear at critical points throughout the system.